1. Field of the Invention
The present invention relates to a cigarette lighter plug, and more particularly, to a cigarette lighter plug that can be inserted into sockets of different dimensions.
2. Description of the Prior Art
Today, more and more people are spending greater amounts of time in automobiles, such as to commute back and forth between work. This increasing amount of time spent in automobiles has lead to an increasing amount of electric equipment that is designed for use in cars. This equipment, which may include such items as vacuums, refrigerators, hands-free cellular telephones, battery chargers, and the like, all use a cigarette lighter socket in the car as a power point. With a suitable cigarette lighter plug for the equipment, a user may simply plug the cigarette lighter plug into the cigarette lighter socket to provide power to the electric equipment.
A cigarette lighter socket is designed as a small cylindrical shell with a bottom. The bottom of the cylinder has a positive terminal connected to a positive terminal of the power in the car. The metallic walls of the cylinder connect to the negative terminal of the power in car to form a negative terminal of the cigarette lighter socket. Corresponding plugs for electric equipment are designed to plug into the cigarette lighter socket and draw electrical power from car. To ensure a good electrical connection between the plug and the socket, the plug must fit snugly with the cigarette lighter socket in the car so as to avoid the plug from disconnecting from the socket due to vibration or shaking.
The typical cigarette lighter plug is designed as a small plastic cylinder. A front end of the plug, corresponding to the bottom of the socket, has a metal protrusion for contacting the positive terminal of the bottom of the cigarette lighter socket. On the side surface of the plug is at least one broad-surfaced metal contact to establish an electrical connection with the negative contact surface of the walls of the socket. When the cigarette lighter is plug is plugged into the cigarette lighter socket, the broad-surfaced contact connects with the negative terminal of the walls of the cigarette lighter socket to electrically connect the electric equipment to power. As noted before, an external diameter of the cigarette lighter plug should tightly match the corresponding dimension of the cigarette lighter socket. When this is so, to disengage the plug from the cigarette lighter socket, friction generated by the broad-surfaced contact must be overcome.
Unfortunately, there are at least two different design specifications for cigarette lighter sockets. For Japanese cars, the diameter of a cigarette lighter socket is about 21 mm. On the other hand, for German cars the diameter is slightly larger, at about 22 mm. The difference between the two dimensions is thus about 1 mm. If a cigarette lighter plug with the smaller external diameter is plugged into the larger diameter socket, a loose fit will result, leading to a poor, intermittent electrical connection. Correspondingly, cigarette lighter plugs with the larger external diameter simply cannot be plugged into the smaller dimensioned cigarette lighter sockets. Consequently, manufacturers must design two types of cigarette lighter plugs to account for the two different external diameters of sockets. This is a nuisance for the manufacturers of electric equipment for cars.
U.S. Pat. No. 6,116,960 provides a cover for cigarette lighter plugs having a small external diameter to solve this problem so that they may be used in larger dimensioned cigarette lighter sockets. However, adding a cover not only increases the costs associated with manufacturing and packing, but the cover can also be easily lost.
It is therefore a primary objective of the present invention to provide a cigarette lighter plug which can be inserted in sockets of different dimensions to solve the above-mentioned problem.
According to claimed invention, a cigarette lighter plug is provided that can be inserted into cigarette lighter sockets of different dimensions. The cigarette lighter plug includes a front housing and a rear housing, a positive contact end installed at a front end of the front housing for contacting a positive terminal of a cigarette lighter socket, and an elastic element encircling a connecting portion of the front housing and the rear housing for contacting a negative terminal of the cigarette lighter socket. When the elastic element contacts the negative terminal of the cigarette lighter socket, the elastic element is electrically connected with the negative terminal of the cigarette lighter socket.
It is an advantage of the present invention that the present invention cigarette lighter plug does not require a cover as an adapter to plug into cigarette lighter sockets of different dimensions.
These and other objectives and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.